Sandblasting is known as one of the techniques for patterning the surface of a substrate such as glass, stone, plastics, ceramics, leather, and wood. Pattern formation by sandblasting is carried out by a process using a stencil in which a rubber sheet, paper, etc. is stuck to the substrate and cut with a cutter, etc. to form a stencil pattern, and an abrasive is made to strike against the substrate to selectively abrade the substrate or a process using a photomask in which a photosensitive layer is provided on the substrate, a mask pattern is formed by photolithography, and an abrasive is made to strike against to selectively abrade the substrate. The former process involves troublesome operations with low working efficiency. On the other hand, the latter photolithographic process achieves high working efficiency and enables fine processing and is effective for production of circuit boards composed of a metallic pattern and an insulating pattern, particularly for the formation of a metallic wiring pattern or an insulating pattern made of ceramics, fluorescence substances, etc. of a plasma display panel.
Photosensitive compositions for the photosensitive layer which have been proposed to date for use in sandblasting include a screen-printable composition comprising a urethane prepolymer having an ethylenically unsaturated group at the terminal, a monofunctional ethylenically unsaturated compound, and a polymerization initiator (see JP-A-60-10242, the term "JP-A" as used herein means an "unexamined published Japanese patent application"), a composition comprising an unsaturated polyester, an unsaturated monomer, and a photopolymerization initiator (see JP-A-55-103554), and a composition comprising polyvinyl alcohol and a diazo resin (see JP-A-2-69754). However, since these photosensitive resin compositions are liquid, they are difficult to handle, and film thickness control is difficult.
A photosensitive composition for sandblasting, which is free from the above disadvantage, mainly comprising a urethane prepolymer having an ethylenically unsaturated group at the terminal and having incorporated therein a cellulose derivative and a polymerization initiator, is proposed in JP-A-6-161098. While the proposed composition has high elasticity, high softness and excellent alkali developability and is superior to the conventional ones in sensitivity and adhesion to a substrate, it is still unsatisfactory in sensitivity, adhesion to a substrate and resistance to sandblasting. It has therefore been demanded to develop a photosensitive composition for sandblasting with improved characteristics.